Dispensing devices for dispensing a foamable product from a container are known in the art. In one example, the dispensing device is disposed on top of a pressurized container containing a foamable product. The dispensing device comprises a flow passage that is coupled at one end to a discharge valve of the pressurized container. A discharge outlet is provided at the other end of the flow passage. To dispense the foamable product, the user presses an actuator part of the dispensing device. This opens the discharge valve of the container. Product then flows into the flow passage and is discharged through the discharge outlet. This discharge occurring from the discharge outlet is driven by the flow of foamable product entering the flow passage from the container, propelled by the vapor pressure of the propellant in the container. The foamable product also expands into a foam within the flow passage as it is being dispensed, such that the volumetric flow rate at the discharge outlet is greater than that at the discharge valve of the container.
After a desired amount of foam has been dispensed, the user releases the actuator, closing the discharge valve of the container, and thereby shutting off the supply of product to the flow passage. However, continued expansion of the product that is already in the flow passage can cause the product to drool out of the discharge outlet.
For present purposes, drool can be defined as an unwanted discharge of foam (or foamable product) from a discharge outlet after dispensing has been stopped by a user, caused by the continued expansion of the foam in the passage between the container-valve and the discharge outlet.
A dispensing device for a foamable product is known from U.S. Pat. No. 6,405,898. It features a system to reduce drool.
In one embodiment, the dispensing device features a nozzle member comprising a flow passage and a movable portion movable between a discharge position and an inactive position. When the movable portion is in the discharge position, the flow passage is in fluid communication with the exterior of the device. When the movable portion is in the inactive position, the flow passage is in fluid communication with a waste product containment region. As such, when the movable portion is in the discharge position and foam is being discharged, the foam is directed to the exterior of the dispensing device. After discharge, and with the movable portion in the inactive position, foamable product (and/or foam) remaining in the flow passage is directed into the waste product containment region.
With the dispensing device of U.S. Pat. No. 6,405,898, there is a chance for undesired leakage of the foamable product from the nozzle member, particularly during a transient period when the movable portion is between the discharge position and the inactive position. Also, an amount of the dispensed product will be collected in the waste product containment region and therefore wasted. These drawbacks are particularly severe with foamable compositions that have high blooming—potentially increasing 5-10 times in volume from the moment they are dispensed to their fully expanded state. For such compositions, the amount of product collected inside the dispensing device will not only be wasted, but it can also expand until it leaks out of the containment region, thereby creating a mess and giving the impression that the dispensing device is not functioning properly.